The app cannot detect the usb device.

Why?

@AmyChen The SanDisk SDDDC4 USB Dual Drive is not supported in the Memory Zone App for iOS. It can only be used with the Files app.

Have you checked our knowledge base articles?
( Get Support for Your SSDs and Flash Products | Sandisk )

Try these.

Have you opened a Support Case?
If not, contact SanDisk Technical Support for assistance.
( Contact Support | Sandisk )

Oh my fun god. It’s ridiculous. Anyway, thank you for your response.

It seems incompatible with your phone.